Electron lens formed by light: A new method for atomic-resolution
electron microscopes

Date:
April 11, 2022
Source:
Tohoku University
Summary:
Researchers have proposed a new method to form an electron lens
that will help reduce installation costs for electron microscopes
with atomic resolution, proliferating their use. Instead of the
electrostatic and magnetic fields employed in conventional electron
lenses, they utilized a light field electron-lens.



FULL STORY ========================================================================== Electron microscopy enables researchers to visualize tiny objects
such as viruses, the fine structures of semiconductor devices,
and even atoms arranged on a material surface. Focusing down the
electron beam to the size of an atom is vital for achieving such high
spatial resolution. However, when the electron beam passes through an electrostatic or magnetic lens, the rays of electrons exhibit different
focal positions depending on the focusing angle and the beam spreads
out at the focus. Correcting this "spherical aberration" is costly and
complex, meaning that only a select few scientists and companies possess electron microscopes with atomic resolution.


========================================================================== Researchers from Tohoku University have proposed a new method to form an electron lens that uses a light field instead of the electrostatic and
magnetic fields employed in conventional electron lenses. A ponderomotive
force causes the electrons traveling in the light field to be repelled
from regions of high optical intensity. Using this phenomenon, a doughnut-shaped light beam placed coaxially with an electron beam is
expected to produce a lensing effect on the electron beam.

The researches theoretically assessed the characteristics of the
light-field electron lens formed using a typical doughnut-shaped light
beam -- known as a Bessel or Laguerre-Gaussian beam. From there, they
obtained a simple formula for focal length and spherical aberration coefficients which allowed them to determine rapidly the guiding
parameters necessary for the actual electron lens design.

The formulas demonstrated that the light-field electron lens generates
a "negative" spherical aberration which opposes the aberration of
electrostatic and magnetic electron lenses. The combination of the
conventional electron lens with a "positive" spherical aberration and a light-field electron lens that offset the aberration reduced the electron
beams size to the atomic scale. This means that the light-field electron
lens could be used as a spherical aberration corrector.

"The light-field electron lens has unique characteristics not seen in conventional electrostatic and magnetic electron lenses," says Yuuki
Uesugi, assistant professor at the Institute of Multidisciplinary
Research for Advanced Materials at Tohoku University and lead author of
the study. "The realization of light-based aberration corrector will significantly reduce installation costs for electron microscopes with
atomic resolution, leading to their widespread use in diverse scientific
and industrial fields," adds Uesugi.

Looking ahead, Uesugi and colleagues are exploring ways for the practical application of next-generation electron microscopes using the light-field electron lens.


========================================================================== Story Source: Materials provided by Tohoku_University. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* A_conceptual_illustration_of_the_light-field_electron_lens ========================================================================== Journal Reference:
1. Yuuki Uesugi, Yuichi Kozawa, Shunichi Sato. Properties of electron
lenses
produced by ponderomotive potential with Bessel and
Laguerre-Gaussian beams. Journal of Optics, 2022; DOI:
10.1088/2040-8986/ac6524 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220411101328.htm

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